Bacteroides-derived isovaleric acid enhances mucosal immunity by facilitating intestinal IgA response in broilers

Background:The interaction between nutrition and immunity plays a vital role in nutrient digestion,absorption,and metabolism during poultry production.Recent studies showed that the gut microbiota contributes to the development of intestinal mucosal immunity.However,the mechanisms by which gut microbes regulate this process remain unclear.Methods:We compared the intestinal mucosal immunity and gut microbiota of Arbor Acre broilers AA(lower mucosal immunity)and Chinese native Wuliang Mountain Black-bone chickens(WLMB)(higher mucosal immunity)using 16S rDNA sequencing,transcriptomic analysis,and immunoglobulin A(IgA)antibody repertoire sequencing.We then combined 16S rDNA sequencing with transcriptomics to identify the key microbes and found that they were positively correlated with IgA production.Next,we transplanted candidate microbes into 1-day-old broiler to explore their role in intestinal mucosal immunity.Finally,we verified the function of candidate microbial metabolites in regulating the immune function of macrophages and the intestinal-epithelial cells(IECs)using in vitro experiments.Results:WLMB performs stronger mucosal immunity than AA,including higher IgA levels,more diverse IgA antibody repertoire,and higher bacterial affinity.Bacteroides was identified as the key microbes related to the intestinal IgA response.Bacteroides transplantation could increase IgA concentration in the duodenal contents by enhancing the expression of IgA,polymeric immunoglobin receptor(PIgR),B cell-activating factor of the TNF family(BAFF),and activation-induced cytidine deaminase(AID)in the duodenum.Additionally,Bacteroides-derived isovaleric acid promoted M2 macrophage polarization of macrophage via mTOR/PPAR-γ/STAT3 signaling pathways and regulated the immunologic function of IECs to produce cytokines,including interleukin(IL)-10,IL-4,BAFF,and transforming growth factor-beta(TGF-β),thus promoting IgA production in B cells by facilitating AID expression.Conclusion:Our study revealed that Bacteroides modulate the intestinal IgA response and maintain gut health in broilers.Bacteroides may be a promising alternative as an immunomodulatory microbial agent for developing nextgeneration probiotics for broiler production.

Bacteroides utilization for dietary polysaccharides and their beneficial effects on gut health

Polysaccharide was a class of macromolecular substance with various bioactive functions.Gut symbiotic microorganisms could utilize the polysaccharides from various sources,thus have important impact on human health.Bacteroides represented one of the dominant colonizers in the human gut.The utilization of polysaccharide by Bacteroides was important for supporting the function and stability of gut microbiota.After the degradation of polysaccharides by Bacteroides,gut microbes could ferment the monosaccharides and oligosaccharides degraded from polysaccharides into some metabolites,such as short-chain fatty acids(SCFAs),amino acids,etc.Among the metabolites,the SCFAs could have beneficial effects on gut health.This review summarized the niches of Bacteroides among gut microbiota,and also described the gene clusters and membrane proteins involved in the utilization processes of polysaccharide by gut Bacteroides.SCFAs could act as energy substrates for intestinal epithelial cells,inhibit histone deacetylases and activate G protein-coupled receptors.In addition,the future perspectives in investigating new degradation pathways for polysaccharide,and using polysaccharides or their metabolites as therapeutic approaches for diseases mediated by the gut dysbiosis were also provided.

Suppression of colorectal tumorigenesis by recombinant Bacteroides fragilis enterotoxin-2 in vivo

AIM To evaluate the impact of recombinant Bacteroides fragilis enterotoxin-2(BFT-2, or Fragilysin) on colorectal tumorigenesis in mice induced by azoxymethane/dextran sulfate sodium(AOM/DSS).METHODS Recombinant pro BFT-2 was expressed in Escherichia coli strain Rosetta(DE3) and BFT-2 was obtained and tested for its biological activity via colorectal adenocarcinoma cell strains SW-480. Seventy C57BL/6J mice were randomly divided into a blank(BC; n = 10), model(AD; n = 20), model + low-dose toxin(ADLT; n = 20, 10 μg), and a model + high-dose toxin(ADHT; n = 20, 20 μg) group. Mice weight, tumor formation and pathology were analyzed. Immunohistochemistrydetermined Ki-67 and Caspase-3 expression in normal and tumor tissues of colorectal mucosa.RESULTS Recombinant BFT-2 was successfully obtained, along with its biological activity. The most obvious weight loss occurred in the AD group compared with the ADLT group(21.82 ± 0.68 vs 23.23 ± 0.91, P < 0.05) and the ADHT group(21.82 ± 0.68 vs 23.57 ± 1.06, P < 0.05). More tumors were found in the AD group than in the ADLT and ADHT groups(19.75 ± 3.30 vs 6.50 ± 1.73, P < 0.05; 19.75 ± 3.30 vs 6.00 ± 2.16, P < 0.05). Pathology showed that 12 mice had adenocarcinoma and 6 cases had adenoma in the AD group. Five mice had adenocarcinoma and 15 had adenoma in the ADLT group. Four mice had adenocarcinoma and 16 had adenoma in the ADHT group. The incidence of colorectal adenocarcinoma in both the ADHT group and the ADHT group was reduced compared to that in the AD group(P < 0.05, P < 0.05). The positive rate of Ki-67 in the ADLT group and the ADHT group was 50% and 40%, respectively, both of which were lower than that found in the AD group(94.44%, P < 0.05, P < 0.05). Caspase-3 expression in the ADLT group and the ADHT group was 45% and 55%, both of which were higher than that found in the BC group(16.67%, P < 0.05, P < 0.05).CONCLUSION Oral administration with lower-dose biologically active recombinant BFT-2 inhibited colorectal tumorigenesis in mice.

Bacteroides fragilis enterotoxin upregulates heme oxygenase-1 in dendritic cells via reactive oxygen species-,mitogen-activated protein kinase-,and Nrf2-dependent pathway

BACKGROUND Enterotoxigenic Bacteroides fragilis(ETBF)causes colitis and diarrhea,and is considered a candidate pathogen in inflammatory bowel diseases as well as colorectal cancers.These diseases are dependent on ETBF-secreted toxin(BFT).Dendritic cells(DCs)play an important role in directing the nature of adaptive immune responses to bacterial infection and heme oxygenase-1(HO-1)is involved in the regulation of DC function.AIM To investigate the role of BFT in HO-1 expression in DCs.METHODS Murine DCs were generated from specific pathogen-free C57BL/6 and Nrf2−/−knockout mice.DCs were exposed to BFT,after which HO-1 expression and the related signaling factor activation were measured by quantitative RT-PCR,EMSA,fluorescent microscopy,immunoblot,and ELISA.RESULTS HO-1 expression was upregulated in DCs stimulated with BFT.Although BFT activated transcription factors such as NF-κB,AP-1,and Nrf2,activation of NF-κB and AP-1 was not involved in the induction of HO-1 expression in BFT-exposed DCs.Instead,upregulation of HO-1 expression was dependent on Nrf2 activation in DCs.Moreover,HO-1 expression via Nrf2 in DCs was regulated by mitogenactivated protein kinases such as ERK and p38.Furthermore,BFT enhanced the production of reactive oxygen species(ROS)and inhibition of ROS production resulted in a significant decrease of phospho-ERK,phospho-p38,Nrf2,and HO-1 CONCLUSION These results suggest that signaling pathways involving ROS-mediated ERK and p38 mitogen-activated protein kinases-Nrf2 activation in DCs are required for HO-1 induction during exposure to ETBF-produced BFT.

Extended role for insertion sequence elements in the antibiotic resistance of Bacteroides

The Bacteroides species are important micro-organisms, both in the normal physiology of the intestines and as frequent opportunistic anaerobic pathogens, with a deeply-rooted phylogenetic origin endowing them with some interesting biological features. Their prevalence in anaerobic clinical specimens is around 60%-80%, and they display the most numerous and highest rates of antibiotic resistance among all pathogenic anaerobes. In these antibiotic resistance mechanisms there is a noteworthy role for the insertion sequence(IS) elements, which are usually regarded as representatives of ‘selfish' genes; the IS elements of Bacteroides are usually capable of up-regulating the antibiotic resistance genes. These include the cep A(penicillin and cephalosporin), cfx A(cephamycin), cfi A(carbapenem), nim(metronidazole) and erm F(clindamycin) resistance genes. This is achieved by outwardoriented promoter sequences on the ISs. Although some representatives are well characterized, e.g., the resistance gene-IS element pairs in certain resistant strains, open questions remain in this field concerning a better understanding of the molecular biology of theantibiotic resistance mechanisms of Bacteroides, which will have clinical implications.

Endophthalmitis caused by Bacteroides fragilis after pars plana vitrectomy and treatment approach

Rationale:Endophthalmitis is an uncommon but serious ocular infection often resulting in probable visual loss.Bacteroides fragilis is a rare cause of endophthalmitis.Patient concerns:A 46-year-old male patient complained of eye pain and low vision after pars plana vitrectomy.Diagnosis:Bacteroides fragilis endophthalmitis after pars plana vitrectomy was diagnosed.Interventions:Pars plana vitrectomy and silicone oil implantation were performed.Outcomes:Early treatment and choice of tamponade in endophthalmitis after pars plana vitrectomy may possibly prevent evisceration and progression of endophthalmitis.Lessons:Bacteroides fragilis can be seen in cases of endophthalmitis after pars plana vitrectomy.

脆弱拟杆菌(Bacteroides fragilis)产肠毒素菌株和非产肠毒素菌株的抗原特性

从腹泻犊牛(62株)、羔羊(2株)和猪(5株)的粪便中获得脆弱拟杆菌产肠毒素株(44株)和非产肠毒素株(25株)。利用微量全细胞凝集试验和凝胶双扩散试验检测,菌株对13株脆弱拟杆菌产肠毒素菌株制备的非吸收兔抗血清有反应。脆弱拟杆菌有多种抗原。根据凝集反应,44株产肠毒素脆弱拟杆菌(ETBE)中有37株(84%)组成13个血清群、25株非产肠毒素脆弱拟杆菌(non—ETBF)中有14株(56%)组成13个血清群中的4个血清群。与凝胶扩散试验的结果比较,大部分菌株对13株抗血清有不同的凝集试验反应模式,从 non—ETBF 中不能区分ETBF。脆弱拟杆菌抗原的异源性促进了个别菌株的变异,这种能力对将来的流行病学和毒力研究是有益的。从腹泻犊牛、羔羊和猪的粪便中分离的ETBF,属于专性厌氧菌。利用肠结扎试验,证明脆弱拟杆菌在犊牛和羔羊中产生一种肠毒素,当给予新生羔羊口服时,证明 ETBF是腹泻病原。根据凝集和凝胶扩散分析,脆弱拟杆菌人株含有多种抗原,许多人株含有热稳定多糖荚膜抗原,可作为一种肠道外感染的毒力因子,有些脆弱拟杆菌人株也含有纤毛。本研究的目的,是根据抗原的不同,区分腹泻家畜的 ETBF 和 non—ETBF 的血清群,是否能从 non—ETBF 中区分 ETBF。

Bacteroides fragilis Supernatant Extracts Enriched in Phenylacetic Acid Induce a Cytotoxic Effect in Mammalian Cells

Bacteroides species are nearly half of the fecal flora community and some are host symbionts crucial to host nutrition and systemic immunity. Among Bacteroides species B. fragilis strains are considered to be the opportunistic ones, being the most isolated anaerobic bacteria in clinical samples. Cell-free supernatants of 65 B. fragilis strains were assayed and they were capable of inducing vacuolating phenotype on Vero cells lineage. The supernatant of the Bacteroides fragilis ATCC 23745 strain was elicited to have the strongest vacuolating effect on Vero cells monolayers and peritoneal macrophages. Some drastic cell alterations were observed, such as a general disorganization of cytoplasm and chromatin condensation, evidencing cell death. By transmission electron microscopy it was confirmed that the vacuoles observed were, in fact, swollen mitochondria. An immunocytochemical assay, TUNEL, was used to confirm this hypothesis and showed that Vero cells and peritoneal macrophages were dying by apoptotic process after exposition of B. fragilis cell-free supernatant. Physical analysis of the apoptotic factor has revealed properties similar to short-chain fatty acids. After gas chromatography and mass spectrometry analysis, phenylacetic acid (PA) was characterized as the major compound present in the most purified active fraction. We believe that the PA is responsible for the pro-apoptotic effect elicited by the supernatant of B. fragilis cultures.

Sugarcane leaves-derived polyphenols alleviate metabolic syndrome and modulate gut microbiota of ob/ob mice

Sugarcane leaves-derived polyphenols(SLP)have been demonstrated to have diverse health-promoting benefits,but the mechanism of action has not been fully elucidated.This study aimed to investigate the anti-metabolic disease effects of SLP and the underlying mechanisms in mice.In the current study,we prepared the SLP mainly consisting of three flavonoid glycosides,three phenol derivatives,and two lignans including one new compound,and further demonstrated that SLP reduced body weight gain and fat accumulation,improved glucose and lipid metabolism disorders,ameliorated hepatic steatosis,and regulated short-chain fatty acids(SCFAs)production and secondary bile acids metabolism in ob/ob mice.Notably,SLP largely altered the gut microbiota composition,especially enriching the commensal bacteria Akkermansia muciniphila and Bacteroides acidifaciens.Oral gavage with the above two strains ameliorated metabolic syndrome(MetS),regulated secondary bile acid metabolism,and increased the production of SCFAs in high-fat diet(HFD)-induced obese mice.These results demonstrated that SLP could be used as a prebiotic to attenuate MetS via regulating gut microbiota composition and further activating the secondary bile acids-mediated gut-adipose axis.

Lower abundance of Bacteroides and metabolic dysfunction are highly associated with the post-weaning diarrhea in piglets

Growing evidences show a direct link between diarrhea and disorders of gut microbiota in pigs.However,whether there are microbial markers associated with post-weaning diarrhea remains unknown.In the current study,we compared the microbial community,functions and metabolites between healthy weaned piglets(group H,n=7)and piglets with post-weaning diarrhea(group D,n=7),in order to find out diarrhea associated microbial markers.Each of 7 fecal samples was collected from H and D piglets(weaned at 21 d and sampled at 26 d).The metagenomic and untargeted metabolomic analysis revealed that the microbial composition,function and metabolic profile in D pigs was considerably reshaped,including the reduced abundance and number of Bacteroides,which significantly correlated with the diarrhea status of host.The carbohydrate metabolism,biosynthesis and metabolism,lipid metabolism,amino acid metabolism,and the activity of glycan and carbohydrates digestion related enzymes showed extensively down-regulated in D pigs compared with H pigs.Diarrhea significantly changed the metabolic profiles of fecal microbiota,and most of the altered metabolites were negatively or positively correlated with the change in the abundance of Bacteroides.In conclusion,the lower abundance of Bacteroides and its associated metabolic dysfunction may be regarded as microbial markers of physiological post-weaning diarrhea in piglets.

Bacteroides ovatus-mediated CD27^(−)MAIT cell activation is associated with obesity-related T2D progression

Type 2 diabetes(T2D)is highly associated with obesity.However,the factors that drive the transition from excessive weight gain to glucose metabolism disruption are still uncertain and seem to revolve around systemic immune disorder.Mucosal-associated invariant T(MAIT)cells,which are innate-like T cells that recognize bacterial metabolites,have been reported to be altered in obese people and to lead to metabolic dysfunction during obesity.By studying the immunophenotypes of blood MAIT cells from a cross-sectional cohort of obese participants with/without T2D,we found an elevation in CD27^(-)negative(CD27−)MAIT cells producing a high level of IL-17 under T2D obese conditions,which could be positively correlated with impaired glucose metabolism in obese people.We further explored microbial translocation caused by gut barrier dysfunction in obese people as a triggering factor of MAIT cell abnormalities.Specifically,accumulation of the bacterial strain Bacteroides ovatus in the peripheral blood drove IL-17^(-)producing CD27−MAIT cell expansion and could be associated with T2D risk in obese individuals.Overall,these results suggest that an aberrant gut microbiota–immune axis in obese people may drive or exacerbate T2D.Importantly,CD27−MAIT cell subsets and Bacteroides ovatus could represent targets for novel interventional strategies.Our findings extend current knowledge regarding the clinical relevance of body mass index(BMI)-associated variation in circulating MAIT cells to reveal the role of these cells in obesity-related T2D progression and the underlying cellular mechanisms.

Cryo-EM structure of L-fucokinase/GDP-fucose pyrophosphorylase(FKP)in Bacteroides fragilis

Dear Editor,L-Fucose(6-deoxy-L-galactose,fucose)is the basic compone nt of a variety of glyca n structures.The fucosylated oligosaccharides participate in a variety of cellular activities,like the cell-cell recognition,selectin-mediated leukocyteendothelial adhesion and the formation of Lewis blood group antigens(Ma et al.,2006).GDP-fucose is an important fucose donor in the process of fucosylated oligosaccharides formation.Two pathways of GDP-fucose synthesis are present in the cytosol of mammalian cells,including the de novo pathway and the salvage pathway(Becker et al.,2003).In the salvage pathway,cells use fucose from the extracellular or lysosomal sources to synthesize GDP-fucose.

Expression of enterotoxigenic Bacteroides fragilis and polyketide synthase gene-expressing Escherichiacoli in colorectal adenoma patients

Objective To investigate the distribution of various bacteria in adenoma tissue of colorectal adenoma(T/CRA),normal colonic mucosa tissue adjacent to the adenoma(N/CRA),and healthy colonic mucosa tissue(N/H)by comparing the number of total bacteria,Bacteroides fragilis(BF),enterotoxigenic Bacteroides

丹酚酸B对小鼠体内抗氧化和肠道微生物群落的影响

为研究丹酚酸B的体内抗氧化性和对小鼠肠道微生物群落的影响,本实验对昆明小鼠灌胃不同剂量丹酚酸B溶液,将小鼠分为丹酚酸B低剂量组(30 mg/kg mb)、丹酚酸B中剂量组(60 mg/kg mb)、丹酚酸B高剂量组(120 mg/kg mb)。42 d后,记录小鼠的体质量变化;计算心脏、肝脏、肾脏、脾脏的脏器指数;检测血液和肝脏的抗氧化指标。结果显示在小鼠肝脏中,中剂量、高剂量和阳性对照组相对于正常组脏器指数显著降低(P<0.05)。肾脏中,高剂量组相对于正常组脏器指数显著降低(P<0.05);阳性对照组相对于正常组极显著降低(P<0.01)。抗氧化指标检测结果显示,和正常组相比较,中剂量组血清中丙二醛(malondialdehyde,MDA)含量显著降低(P<0.05),高剂量组和VC组血清中MDA含量极显著降低(P<0.01),高剂量组肝脏中MDA含量显著降低(P<0.05)。高剂量组和VC组血清中GSH含量显著增加(P<0.05)。通过高通量测序技术分析可知,小鼠肠道菌群结构以拟杆菌门(Bacteroidetes)、厚壁菌门(Firmicutes)、变形菌门(Proteobacteria)、疣微菌门(Verrucomicrobia)、放线菌门(Actinobacteria)为各组的优势菌门。根据LEfSe分析发现相对正常组,3组给药组中Bacteroides vulgatus和Parabacteroides distasonis两个菌种相对丰度显著增加(P<0.05),相对丰度随药物浓度增加而降低。丹酚酸B可以提高小鼠体内抗氧化能力,改善小鼠肠道环境,增加有益菌,该发现为丹酚酸B治疗心血管疾病提供新的研究思路。

牙髓类杆菌的分离、培养、鉴定

试验目的是为寻找口腔内产黑色素类杆菌群中新的菌种一牙髓类杆菌（Bacteroides·endodontalis）,试验选择牙髓腔感染的成年患者80例,儿童患者（14岁以下）18例,在厌氧环境下用光滑髓针加棉捻方法收集标本,经厌氧培养,对在CDC琼脂培养基（含0.01％Vitk3及0.05％氯化血红素）上生长的产黑色素的菌落进行生化,直接血凝试验、气相色谱分析。

肿瘤粪菌疗法

<正>人类肠道含有丰富的细菌,其数量是人体细胞数量的10倍,从上往下细菌越来越多:十二指肠102~103/ml,空肠103~105/ml,回肠105~107/ml,大肠1010~1012/ml。肠道菌群(gut microbiota)的重量约占人体体重的2磅左右,其基因量约3百万个基因,是人体基因量的100倍。肠道菌群的细菌组成,在门级(phylum level)水平上。

金定鸭盲肠厌氧菌的研究

正常生理条件下,动物肠道中寄居着大量的微生物,构成了肠道正常菌群。正常菌群对动物宿主的生长、发育和衰老,对营养物质的吸收和消化,对于宿主的免疫应答和对各种致病因素的抗性等,都起着不可忽视的作用。金定鸭是我国著名的蛋用鸭,平均年产蛋300枚、蛋质好、用途广。该鸭种适应性强。

几种拟杆菌质粒提取方法的比较

本文介绍了4种拟杆菌质粒的提取方法,并对它们做了比较,根据作者的体会,指出了每种方法的特点和操作时应注意的问题。

痤疮型多囊卵巢综合征患者肠道菌群分析

目的以基于16S rDNA高通量测序技术分析痤疮型多囊卵巢综合征患者的肠道菌群结构特征。方法以痤疮综合评分系统(GAGS)评价患者痤疮程度,收集健康女性(HC,n=10)、多囊卵巢综合征女性(NA-PCOS,n=10)和中重度痤疮多囊卵巢综合征女性(MSA-PCOS,n=10)新鲜粪便,扩增细菌16S rDNA V3-V4片段并对其进行测序,分析受试者肠道菌群的组成特征及其与临床参数之间的相关性。结果与对照组相比,PCOS患者肠道菌群多样性降低(P<0.05),粪便中Bacteroides相对丰度显著高于健康组(P<0.001),Prevotella和Faecalibacteruim显著减少(P<0.05);MSA-PCOS患者肠道菌群中Bacteroides相对丰度显著高于NA-PCOS患者(P<0.01);Bacteroides与睾酮、炎症因子、血脂异常呈正相关(P<0.05)。结论肠道菌群紊乱可能加剧PCOS患者代谢和内分泌紊乱进而导致痤疮皮损加重。

Gut microbiome composition can predict the response to nivolumab in advanced hepatocellular carcinoma patients

BACKGROUND Immunotherapy has revolutionized the clinical outcomes of intractable cancer patients.Little is known about the intestinal nonpathogenic bacterial composition of hepatocellular carcinoma(HCC)patients treated by immunotherapy.AIM To determine whether there is a correlation between gut bacterial composition and prognosis in HCC patients.METHODS From September 2019 to March 2020,we prospectively collected fecal samples and examined the gut microbiome of 8 advanced HCC patients treated with nivolumab as a second-or third-line systemic treatment.Fecal samples were collected before the start of immunotherapy.Fecal samples of patients with progression during treatment were collected at the time of progression,and fecal samples of patients who showed good response to nivolumab were collected after 5-7 mo as follow-up.Metagenomic data from 16S ribosomal RNA sequencing were analyzed using CLC Genomics Workbench.Microbiome data were analyzed according to therapeutic response.RESULTS All 8 patients were male,of which 6 had underlying chronic hepatitis B.A higher Shannon index was found in the responders than in the non-responders after nivolumab therapy(P=0.036).The unweighted beta diversity analysis also showed that the overall bacterial community structure and phylogenetic diversity were clearly distinguished according to therapeutic response.There was no significant difference in the diversity or composition of the patient gut microbiome according to the immunotherapy used.Several taxa specific to therapeutic response were designated as follows:Dialister pneumosintes,Escherichia coli,Lactobacillus reteri,Streptococcus mutans,Enterococcus faecium,Streptococcus gordonii,Veillonella atypica,Granulicatella sp.,and Trchuris trichiura for the nonresponders;Citrobacter freundii,Azospirillum sp.and Enterococcus durans for the responders.Of note,a skewed Firmicutes/Bacteroidetes ratio and a low Prevotella/Bacteroides ratio can serve as predictive markers of non-response,whereas the presence of Akkermansia species predicts a good response.CONCLUSION The current presumptive study suggests a potential role for the gut microbiome as a prognostic marker for the response to nivolumab in treatment of HCC patients.